Angioplasty procedures have gained wide acceptance in recent years as efficient and effective methods for treating types of vascular disease. In particular, angioplasty is widely used for opening stenoses in the coronary arteries and is used for treating stenoses in other vascular regions.
One widely used form of angioplasty makes use of a dilatation catheter which has a inflatable balloon at the distal end and a guide wire lumen within at least a portion of the catheter shaft. Typically, a guide wire is inserted through the vascular system to a position near the stenoses, leaving a proximal portion of the guide wire extending from the patient. The proximal guide wire portion is threaded through the dilatation catheter guide wire lumen, and the dilatation catheter is advanced through the vascular system over the guide wire to a position near the stenoses. The treating physician manipulates the dilatation catheter until the balloon is positioned across the stenoses. The balloon is then inflated by supplying fluid under pressure through an inflation lumen in the catheter to the balloon. The inflation of the balloon widens the vessel lumen through the stenosed area by pressing the inflating balloon wall against the lesion inside wall.
One class of dilatation catheters, termed “Single Operator Exchange” (SOE) or “Rapid Exchange” catheters, have only a short, distal guide wire lumen, to allow for easy removal and replacement of catheters while requiring only a short length of guide wire extending proximally from a patient. These catheters include a distal portion having multiple desired attributes. The catheter distal portion preferably has a small profile or cross-sectional area and is very flexible, to allow for traversing narrow and tortuous vessel paths. The distal portion may also require a guide wire tube having a lumen, which increases the profile. The guide wire lumen preferably has a lubricious inside wall to ease movement of the catheter over the guide wire.
Many current SOE catheters have outer polyethylene tubes and inner polyethylene guide wire tubes inserted therein. An orifice can be created in the side of the outer tube wall and the inner tube inserted through the orifice. The inner tube is inserted so as to extend longitudinally through the lumen of the outer tube. On one side of the inner tube, distal of the orifice, the outside surface of the inner tube runs close to the inside surface of the outer tube. On the opposite direction, proximal of the orifice, the outside surface of the inner tube runs along the outside surface of the outer tube, in a crimped or buckled hollow surface region. The close proximity of the tube surfaces suggests bonding using adhesive or heat bonding. Heat bonding is preferred to adhesive bonding.
Polyether block amide (PEBA) tubes have greater flexibility than polyethylene tubes, and it would be desirable to use PEBA tubes for the outer tubes. It is very desirable to have the inner and outer tubes formed of mutually compatible materials to enable heat bonding. Use of PEBA for guide wire inner tubes would provide such heat bonding compatibility. PEBA is generally less lubricious than polyethylene, however, making polyethylene a more desirable material for forming the inner tube. Lubricity is important for providing a low friction inner surface for accepting a guide wire. What would be desirable is a catheter allowing for use of a more flexible outer tube while retaining the benefits of a more lubricious inner tube while allowing high-quality heat bonding between the two tubes.